President Nixon tells a White House news conference, March 15, 1973, that he will not allow his legal counsel, John Dean, to testify on Capitol Hill in the Watergate investigation and challenged the Senate to test him in the Supreme Court. AP Photo.

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President Nixon is widely known for keeping an “enemies list,” which became public during the Watergate investigations. According to a secret internal memo titled “Dealing With Our Enemies,” the list’s official purpose was to “screw” Nixon’s personal and political foes. “This memorandum addresses the matter of how we can maximize the fact of our incumbency in dealing with persons known to be active in their opposition to our Administration; stated a bit more bluntly -- how we can use the available federal machinery to screw our political enemies.” This was accomplished with onerous tax audits by the IRS, and by manipulating the availability of grants and federal contracts.

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Article II of Nixon's impeachment:

“This conduct has included one or more of the following: He has, acting personally and through his subordinates and agents, endeavored to obtain from the Internal Revenue Service, in violation of the constitutional rights of citizens, confidential information contained in income tax returns for purposed not authorized by law, and to cause, in violation of the constitutional rights of citizens, income tax audits or other income tax investigations to be initiated or conducted in a discriminatory manner.”